Pyrotechnic timers



Oct. 4, 1960 H. ELLERN EIAL PYROTECHNIC TIMERS 2 Sheets-Sheet 1 FiledJuly 14, 1958 HG. 5 23 INVENTORS.

HERBERT ELLERN DONALD E. OLANDER ATT' Oct. 4, 1960 H. ELLERN ETALPYROTECHNIC TIMERS 2 Sheets-Sheet 2 Filed July 14, 1958 Ill INVENTORS.HERBERT ELLERN BY DONALD E OLANDER ATTY.

2,954,735 Patented Oct. 4, 1960' PYRGTECHNIC TMERS Herbert Ellern,Ferguson, and Donald E. Olander, Florissant, Mo., assignors to UniversalMatch Corporation, Ferguson, Mo., a corporation of Delaware Filed July14, 1953, Ser. No. 748,227

Claims. (Cl. l0285) This invention relates in general to ordnancedevices and, more particularly, to certain new and useful improvementsin pyrotechnic timers.

In order to time a series of events for pyrotechnic or explosivepurposes in an interval exceeding several seconds and to include the oneto five minute range, it is customary to employ delay trains whichusually consist of either a tubular cord having a core of modified blackpowder, or a powder-impregnated string. These delay trains provide alinearly advancing flame and are fabricated in lengths of severalhundred feet so that delay times ranging from a few seconds to manyminutes can be achieved, depending upon the length of cord or stringused. However, fuses of this character are particularly vulnerable tomoisture, and are also greatly dependent upon ambient gas pressure,including the relatively large quantities of gases chemically createdduring burning. Consequently, fuses of this type are generallyunsuitable for packaged items and especially for the relative precisionand reliability needed in military applications. Moreover, for delaytimes within the range of several seconds to several minutes, the lengthof the fuse becomes excessive and since, in military pyrotechnicaldevices, the packaging and space requirements are limited, thearrangement of the fuse becomes a serious problem due to the necessityof preventing pressure build-up within the delay powder-column and alsothe need for adequate dissipation of heat as the delay train isconsumed. Therefore, if the delay train is packaged in a relativelysmall amount of space, the heat and gas pressure gencrated may speed upthe pyrotechnica-l reaction to a multiple of its normal rate. Compressedpowdercolumns of low-gassing powder mixtures are equally unsuitable ifcolumns exceeding a few inches in length are employed. These problemshave, thus, up to now, remained unsolved, particularly in view of theadditional requirement that the entire delay system must be hermeticallysealed for purposes of surveillance, as well as to achieve unvaryingfunction at all atmospheric pressures and to preventexcessiveheat-accumulation within the delay system and the adjoiningcomponents in association with which the delay system is used.

It is, therefore, the primary object of the present invention to providea pyrotechnic timer which is completely enclosed and hermetically sealedto the outside and which will function reliably throughout a relativelywide temperature range and over an extended time-interval.

It is also an object of the present invention to provide a pyrotechnictimer of the type stated which is relatively small in volumeand at thesame time will prevent speedup of the pyrotechnical reaction due toexcessive gas pressure build-up or heat.

It is an additional object of the present invention to provide apyrotechnic timer of the type stated which will furnish relatively longdelay times notwithstanding that the device is of relatively smallvolume.

It is a further object of the present invention to provide a pyrotechnictimer of the type stated which permits a selection of operating delaytimes.

It is another object of the present invention to provide a pyrotechnictimer of the type stated which is relatively simple in construction andis extremely reliable in operation.

With the above and other objects in view, my invention resides in thenovel features of form, construction, arrangement, and combination ofparts presently described and pointed out in the claims.

In the accompanying drawings (two sheets)- Fig. 1. is a perspective viewof a pyrotechnic timer constructed in accordance with and embodying thepresent invention;

Fig. 2 is a top plan view thereof;

Fig. 3 is a sectional view taken along line 3-3 of Fig. 1, the devicebeing shown unfilled in order that the interior construction may be moreclearly illustrated;

Fig. 4 is a sectional view taken along line 4--4 of Fig 3;

Fig. 5 is a sectional view taken along line 55 of Fig. 2;

Fig. 6 is a front elevational view partly broken away and in section,and showing the device as it appears when filled wit-h pyrotechniccomposition and noncombustible fibrous material;

Fig. 7 is a sectional view taken along line 77 of Fig. 6;

Fig. 8 is an exploded fragmentary perspective view illustrating theconstruction of the bottom or terminal end of the pyrotechnic timer; and

Fig. 9 is a diagrammatic view of a modified form of pyrotechnic timer.

Referring now in more detail by reference characters to the drawingswhich illustrate a practical embodiment of the present invention, Adesignates a pyrotechnic timer comprising a hollow cylindrical canister1 provided on its opposite ends with. snug-fitting top and bottom coverdiscs 2, 3. Interposed between the cover disks 2, 3, and canister 1 areannular sealing rings 4, 5, so as to form an hermetically sealedcontainer, and the cover disks 2, 3, are centrally recessed and providedwith aligned holes 6, 7, for receiving an elongated bolt 8 having a nut8' thereon by which the cover disks 2, 3, are held snugly against thecanister 1. Formed in the inside face of the top cover disk are threerecesses 9, 10, and 11, the recesses 10, 11 comunicating with each otherby means of a connecting groove 12. Similarly formed in the inside faceof the bottom cover disk 3 are recesses 13, 14, and 15, which are,respectively, axially aligned with the recesses 9, 10, 11, and therecesses 13, 14, communicate with each other through a groove 16.

Secured at its opposite ends in the recesses 9, 13 and extending betweenthe cover disks 2, 3 is a tube 17, preferably of copper, and provided onits upper or starting end with a series of vent holes 18. Adjacent theupper end of the tube 17 the cover disk 2 is provided with a hole 19 forreceiving a potted squib 20 which is sealed in place by a superimposedbarrier disk 21, and extending outwardly from the squib 20 and throughthe barrier disk 21 are electrical starter wires 22. While the squib 2Gis illustrated as being electrically initiated, it should be understoodthat a percussion or heat-sensitive primer may also be used. Mounted inthe recesses 13, 14 and groove 16 is a plate-like combustiblepyrotechnic crosslink 23 which is disposed across the bottom end of thetube 17 and also across hte bottom or starting end of a tube 24, similarto the tube 17 previously described, and provided at its bottom end witha plurality of vent holes 25. The tube 24 is positioned within therecesses 14, 10 and extends in spaced parallel relation to the tube 17.

' 3 and disposed across the upper or terminal end of the tube 24 is apyrotechnic cross-link 26, the latter being mounted in the recesses 10,11 and groove 12. The cover disk 2 is provided with a tapped hole 27 forreceiving a threaded plug 28 for allowing fire tra-nSfe'r to the outsideand for purposes presently and more fully appearing. Mounted in therecess 11 and endwise across the pyrotechnic cross-link 26 is a thirdtube 29, similar to the tubes 17,24, and provided at its upper orstarting end with a plurality of vent holes 30. The tube 29,furthermore, extends downwardly into the recess 15, and the cover disc3is bored for receiving a sleeve 31 which is adtures. The cross-links 23,26, are formed of a low gass ing first-fire composition. In thisconnection, it should be noted thatsuch powder mixtures are well known,as shown in United States Patents Nos. 2,450,892, 2,457,860, and2,696,429, and are, therefore, not described in detail. Moreover, thepresent invention does not reside in the 'use of any specific chemicalcomposition or compositions,

but, rather, resides in the mechanical arrangement and utilizations ofmixtures of the general type specified.

The space surrounding the tubes 17, 24, 29, is preferably filled withnoncombustible flufiy fibrous material 34, such as mineral wool orexpanded mica. The tubes 17, 24, 29, are of smaller diameter than therecesses 9, 19, 111, 13, 14, 15, and the spaces between the'tubes 17,24, 29, and the walls of the recesses 9, 10, 11, 13, 14, 15, are alsopacked with fine metal wool 35 or other noncombustible material.Inwardly of and adjacent the barrier disk 32, the sleeve 31 may befilled with a gaseous propellant type material 36 which, when ignited,will blow out the barrier disk 32. Alternatively, if desired, theterminal fire-transfer from the tube 29 may be eliected by means of apermanently sealed disk having a hot pyrotechnic composition of theso-called first fire type on the inside and a similar composition orheat sensitive primer on the outside.

In use, the squib 20 is fired from a suitable source of current (notshown) which is connected to the wires 22. so as to ignite thecomposition 33 which progressively burnswithin the tube 17; As the flameor glow front reaches the end of the tube 17, it will ignite thepyrotechnic cross-link 23 which will, in turn, burn and ignite thecomposition 33 at the lower or starting end of the tube 24. Thus, thepyrotechnic cross-link 26 provides lateral flame and glow transferbetween the terminal end of the tube 17 and starting end of the tube 24.The glow front then progressively advances through the tube 24 to itsterminal end, then laterally across the pyrotechnic cross-link 26, andthereafter downwardly through the tube 29 so as to ignite thecomposition 36 and blow out the barrier disk 32. The composition 36will, of course, provide fire-transfer to the outside for purposes ofigniting a suitable rnain charge.

- The presence of the holes 18, 25, 30, at the starting ends of thetubes 17, 24, 29, permits venting of the reaction-gases into the'maincavity of the canister 1 and, therefore, prevents build-up of excess gaspressure within the tubes and allows steady progression of the reactionwithout undue acceleration. 'The packing material 35 prevents falsefire-transfer between vent holes since it will cool escaping gas as wellas entrap hot or ignited solid particles which may be emitted from thevent holes as the reaction in the tubes proceed. Sincethe're is asignificant amount of radiation and convection of heat lflromtube-to-tube, the material 34 will reflect and absorb eat.

fluffy, it occupies a relatively small volume and thus 1 into which thereaction gases can expand;

At the same time, however, since the material is If desired, the plug 28may be removed to allow firetransfer to the outside at the terminal endof the tube 24, thus providing a choiceof two periods of delay.

Furthermore, if desired, upon removal of the plug 23,

a suitable squib containing a gaseous, propellant composition may beinserted into the hole 27. It will be apparent, however, that plugs orsimilar sealing members may be secured within the cover disks 2, 3, atthe terminal end of each tube/17, 24, 29 so that various delay periodsmaybe selected. Moreover, while the canister 1 is illustrated ascontaining three tubes or delay columns,

it will be obvious that. a greater or lesser number of tubes can beemployed therein. v 4 7 It is also possible to arrange several completedelay trains within a single'canister .37.which are parallel connected,as diagrammatically illustrated in Fig. 9. The tubes 38, 39, 40, 41, 42,43, are mounted in the canister 37 in the same manner as the tubes17,24, 29, previously described, and the upper or starting'end of thetube 38 is connected to the upper ends of the tubes 39, 42 bypyrotechnic cross-links 44, 45. At its lower or terminal end the tube 38is closed oif by a suitable,

plug or disk 46 for optionally permitting fire transfer to the outsideof canister 37. The lower end of the tube 39 is connected to the lowerend of the tube 40 by a pyrotechnic cross-link 47, and, similarly, theupper end of the tube 40 is connected to the upper end of the tube 41 bya pyrotechnic cross-link 48. The terminal end of the tube 41 is closedoff by a plug or disk 49 similar to the plug 46. The lower ends of thetubes 42, 43 are connected by a pyrotechnic cross-link 50 and the upperend of the tube 43 closed by a plug 51. The initiation of the delaytrains may be eiiected by a squib 52, similar to the squib 20. Uponfiring of the squib 52, the crosslinks 44, 45 and powder in the tube 38will ignite and advance the glow front in each train. Since the plugs46, 49, 5-1 close 01f the terminal points of each delay train, anypreselected plug may be removed to allow fire transfer to the outside,depending upon the delay time desired.

Pyrotechnic timers of the foregoing type will function reliably attemperatures between 100. F. and +200 F. and will furnish delay times ofas much as five minutes, depending upon the powder'used. At the sametime, the delay trains can be housed in a sealed container of relativelysmall volume. Furthermore, while there is no specific maximum limit tothe delay time furnished by the present pyrotechnic timers, it has beenfound that for delay times considerably in excess of five minutes, thesize of the canister 1 is necessarily quite large and bulky. g

It should be understood that changes and modifications in the form,construction, arrangement, and combination of the several parts of thepyrotechnic timer may be made and substituted for those herein shown anddescribed without departing from the nature and principle of ourinvention.

Having thus described our invention, what we claim i and desire tosecure by-Letters Patent is:

l. A pyrotechnic timer comprising a closed canister having rigid wallsof sufi'icient strength to withstandthe expansive forces generated bythe pyrotechnic reaction when initiated, 'a plurality of spaced tubespermanently and rigidly mounted within said canister and each containinga pyrotechnic delay composition, said tubes collectively occupyingsubstantially less than the total space within the container, each saidtube being vented atone end to'the interior of the canister, andpyrotechnic flametransfer means connecting the ends of said tubes insuch a manner as to form at least one continuous pyrotechnic delaytrain. i

2. A pyrotechnic timer comprising a closed canister having rigid wallsof 'sufiicient strength to withstand the expansive forces generated bythe pyrotechnic reaction when initiated, a'plurality of'spaced tubesmounted 'permanently and rigidly within said canister and eachcontaining a pyrotechnic delay composition, each said tube being ventedat one end to the interior of the canister, and a pyrotechnic cross-linkdisposed across the ends of the tubes in such a manner as to form atleast one continuous pyrotechnic delay train.

3. A pyrotechnic timer comprising a closed canister having rigid Wallsof sufiicient strength to Withstand the expansive forces generated bythe pyrotechnic reaction when initiated, a plurality of spaced tubesmounted permanently and rigidly within said canister and each containinga pyrotechnic delay composition, each said tube being vented at one endto the interior of the canister, a noncombustible fluffy materialdisposed in said canister in the space surrounding said tubes, and apyrotechnic cross-link positioned across the ends of the tubes in such amanner as to form at least one continuous pyrotechnic delay train.

4. A pyrotechnic timer comprising a closed canister having rigid Wallsof sufficient strength to withstand the expansive forces generated bythe pyrotechnic reaction when initiated, at least one tube mountedpermanently and rigidly within said canister and containing apyrotechnic delay composition, said tube being vented at one end to theinterior of the container, a noncombustible fluffy material disposed inand substantially filling said canister, and means for igniting saidpyrotechnic delay composition.

5. A pyrotechnic timer comprising a closed canister, a plurality ofspaced tubes mounted within said canister and each containing apyrotechnic delay composition, each said tube being vented at one end tothe interior of the container, a noncombustible fluify material disposedin said canister in the space surrounding said tubes, a pyrotechniccross-link positioned across the ends of said tubes in such a manner asto form at least one continuous pyrotechnic delay train having aninitial and terminal end, means for effecting fire transfer from saidterminal end to the exterior of the canister, and a closure member onsaid canister for optionally permitting fire transfer to the exterior ofsaid canister intermediate the initial and terminal end of the delaytrain.

6. A pyrotechnic timer comprising a closed canister provided withend-closure disks, said disks being provided with a plurality ofrecesses presented toward the interior of said canister, groove meansconnecting said recesses, a plurality of spaced tubes mounted withinsaid canister and having their opposite ends projecting into saidrecesses, each tube containing a pyrotechnic delay composition and eachbeing vented at one end to the interior of the container, a plurality ofpyrotechnic crosslinks positioned in said recesses and grooves anddisposed across the ends of said tubes in such a manner as to form atleast one continuous pyrotechnic delay train having an initial andterminal end, means at said initial end for igniting said delay train,and means at said terminal end for effecting fire transfer to theexterior of the canister.

7. A pyrotechnic timer comprising a closed canister provided withend-closure disks, said disks being provided With a plurality ofrecesses presented toward the interior of said canister, groove meansconnecting said recesses, a plurality of spaced tubes mounted Withinsaid canister and having their opposite ends projecting into saidrecesses, each tube containing a pyrotechnic delay composition and eachbeing vented at one end to the interior of the container, anoncombustible material filling said canister in the space surroundingsaid tubes, a plurality of pyrotechnic cross-links positioned in saidrecesses and grooves and disposed across the ends of said tubes in sucha manner as to form at least one continuous pyrotechnic delay trainhaving an initial and terminal end, means at said initial end forigniting said delay train, and means at said terminal end for effectingfire transfer to the exterior of the canister.

8. A pyrotechnic timer comprising a closed canister having rigid wallsof sufficient strength to Withstand the expansive forces generated bythe pyrotechnic reaction when initiated, a plurality of spaced tubesmounted permanently and rigidly within said canister and each containinga pyrotechnic delay composition, each said tube being vented at one endto the interior of the canister, loosely packed steel wool disposed insaid canister in the space surrounding said tubes, a pyrotechniccrosslink positioned across the ends of the tubes in such a manner as toform at least one continuous pyrotechnic delay train.

9. A pyrotechnic timer comprising a closed canister having rigid wallsof sufficient strength to Withstand the expansive forces generated bythe pyrotechnic reaction when initiated, a plurality of spaced tubesmounted permanently and rigidly within said canister and each containinga pyrotechnic delay composition, each said tube being vented at one endto the interior of the canister, a body of loosely packed material ofthe class consisting of mineral wool, metal wool, and expanded mica,said body of material being disposed in said canister in the spacesurrounding said tubes, and a pyrotechnic crosslink positioned acrossthe ends of the tubes in such a manner as to form at least onecontinuous pyrotechnic delay train.

10. A pyrotechnic timer comprising a closed canister having rigid Wallsof sufficient strength to withstand the expansive forces generated bythe pyrotechnic reaction when initiated, at least one rigid-Walled tubemounted permanently and rigidly within the said canister and containinga pyrotechnic delay composition, said tube being vented at one end tothe interior of the container, a noncombustible fluffy fibrous materialdisposed in and substantially filling said canister while providing asubstantial amount of interstitial space into which the gases ofcombustion may expand as the pyrotechnic reaction pro gresses, and meansfor igniting said pyrotechnic delay composition.

References Cited in the file of this patent UNITED STATES PATENTS 39,682Schenkl Aug. 25, 1863 617,539 Pain Jan. 10, 1899 1,237,816 Rimailho Aug.21, 1917 1,346,454 Holt July 13, 1920 1,481,677 Blashill Jan. 212, 19241,770,921 Hitt July 22, 1930 1,847,268 Schladt Mar. 1, 1932 2,359,777Moore Oct. 10, 1944 2,757,566 Towell Aug. 7, 1956 FOREIGN PATENTS 4,179Great Britain 1905 5,654 Great Britain 1909 22,321 Great Britain 1911439,023 France Mar. 29, 1912

